Lenovo ThinkServer RD240 MegaRAID SAS Software User Guide - Page 356
RAID 1, RAID level, raw capacity, read policy, coercion mode is applied to reduce the capacity.
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Page 356 highlights
RAID 1 RAID 5 RAID 6 RAID 10 RAID 50 RAID 60 RAID level raw capacity read policy Uses data mirroring on pairs of drives so that data written to one drive is simultaneously written to the other drive. RAID 1 works well for small databases or other small applications that require complete data redundancy. Uses data striping and parity data across three or more drives (distributed parity) to provide high data throughput and data redundancy, especially for applications that require random access. Uses data striping and parity data across three or more drives (distributed parity) to provide high data throughput and data redundancy, especially for applications that require random access. RAID 6 can survive the failure of two drives. A combination of RAID 0 and RAID 1 that uses data striping across two mirrored drive groups. It provides high data throughput and complete data redundancy. A combination of RAID 0 and RAID 5 that uses data striping across two drive groups with parity data. It provides high data throughput and complete data redundancy. A combination of RAID 0 and RAID 6 that uses data striping across two drive groups with parity data. It provides high data throughput and complete data redundancy. RAID 60 can survive the failure of two drives in each RAID set in the spanned drive group. A virtual drive property indicating the RAID level of the virtual drive. ThinkServer SAS controllers support RAID levels 0, 1, 5, 6, 10, 50, and 60. A drive property indicating the actual full capacity of the drive before any coercion mode is applied to reduce the capacity. A controller attribute indicating the current Read Policy mode. In Always Read Ahead mode, the controller reads sequentially ahead of requested data and stores the additional data in cache memory, anticipating that the data will be needed soon. This speeds up reads for sequential data, but there is little improvement when accessing random data. In No Read Ahead mode, read ahead capability is disabled. In Adaptive Read Ahead mode, the controller begins using read ahead if the two most recent drive accesses occurred in sequential sectors. If the read requests are random, the controller reverts to No Read Ahead mode. B-8 Glossary
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